This invention relates to chart recorders such as those in widespread use in industrial process control, and elsewhere.
Typically, a chart in roll or fan-fold form is driven at a uniform rate past a recording station at which are located one or more recording pens. Through appropriate interfaces, these recording pens are displaced transversely in a representation of data received at one or more data input ports. Optionally, alphanumeric data may also be recorded. In this way, a permanent record is achieved of key process parameters over a defined time period. Using common chart roll lengths of 15 or 30 meters and a typical chart speed for process control, it is possible to record data on a single chart covering a period of 30 or 60 days.
A chart strip, whether in roll or fan-fold form, provides accurate, long-term storage of monitored process parameters with a high degree of reliability and at relatively low cost. It is a disadvantage of charts, however, that reviewing the recorded data will necessitate careful manipulation of perhaps 15 or 30 meters of chart strip. This can be cumbersome and time-consuming whether the chart is in roll or fan-fold form.